Effects on plasma lipids and fatty acid composition of very low fat diets enriched with fish or kangaroo meat

The effects of very low fat diets (<7% energy) enriched with different sources of long chain (C20 and C22) polyunsaturated fatty acids (PUFA) on plasma lipid levels and plasma fatty acids (PUFA) on plasma lipid levels and plasma fatty acid composition were studied in 13 healthy volunteers. Three diets provided 500 g/day of tropical Australian fish (rich in arachidonic acid and docosahexaenoic acid), southern Australian fish (rich in docosahexaenoic acid) or kangaroo meat (rich in linoleic and arachidonic acids). The fourth diet was vegetarian, similarly low in fat but containing no 20- and 22-carbon PUFA. Subjects ate their normal or usual diets on weeks 1 and 4 and the very low fat diets in weeks 2 and 3. Weighed food intake records were kept, and weeks 2, 3 and 4 were designed to be isoenergetic with week 1. Plasma cholesterol levels fell significantly on all diets within one week. There were reductions in both low density (LDL) and high density lipoprotein (HDL) cholesterol levels, with effects on HDL cholesterol being more consistent. There were no consistent or significant effects on total triglyceride levels despite the high carbohydrate content of the diets. On all diets the percentage of linoleic acid fell in the plasma phospholipid and cholesteryl ester fractions, while the percentage of palmitic acid in the phospholipids and cholesteryl esters and palmitoleic acid in the cholesteryl ester fraction rose on all diets. The percentage of arachidonic acid rose in the phospholipid and cholesteryl esters on the two diets that were good sources of this fatty acid (tropical fish and kangaroo meat). The percentage of docosahexaenoic acid also rose on the two diets that were the richest sources of this fatty acid (the fish diets), and the percentage of eicosapentaenoic acid rose in the phospholipid and cholesteryl esters in proportion to the dietary level of this fatty acid (southern fish > kangaroo > tropical fish). The changes in fatty acid composition were almost completely reversed within seven days of returning to the usual higher fat diets.     

A semiautomated enzymatic method for determination of nonesterified fatty acid concentration in milk and plasma

An enzymatic assay for the determination of non-esterified fatty acid concentrations in milk and plasma is described. The procedure is semiautomated for use with a plate luminometer or plate spectrophotometer and enables routine batch processing of large numbers of small samples (≤5 μL). Following the activation of nonesterified fatty acids (NEFA) by acyl-CoA synthetase, the current assay utilizes UDP-glucose pyrophosphorylase to link inorganic pyrophosphate to the production of NADH through the reactions catalyzed by phosphoglucomutase and glucose-6-phosphate 1-dehydrogenase. With this assay sequence the formation of NADH from NEFA is complete within 50 min at 37°C. Enzymatic spectrophotometric techniques were unsuitable for NEFA determination in human milk due to the opacity of the sample. The use of the NADH-luciferase system has overcome this problem, allowing the enzymatic determination of NEFA in human milk. Sample collection and treatment procedures for milk and plasma have been developed to prevent enzymatic lipolysis and to limit interference from enzymes present in milk. The recovery of palmitic acid added to milk and plasma samples was 94.9±2.9 and 100±4.5%, respectively. There was no difference (P=0.13) in plasma NEFA concentrations determined by the current method and a commercially available enzymatic spectrophotometric technique (Wako NEFA-C kit). Plasma NEFA concentrations determined by gas chromatography were 28% higher compared to both the Wako NEFA-C kit and the current method.     

Effect of dietary n-9 eicosatrienoic acid on the fatty acid composition of plasma lipid fractions and tissue phospholipids

n-9 Eicosatrienoic acid (ETrA), also known as Mead acid, is a minor fatty acid in essential fatty acid (EFA)-sufficient healthy subjects but is found at increased levels in EFA deficiency. This study examined the influence of dietary ETrA from a biological source on plasma and tissue ETrA. A synthetic fat-free diet was prepared to which was added Mut 48 oil which contains 19% ETrA (wt%) as well as other n-9 fatty acids. Blends of vegetable oils were used to achieve overall diets with 5% fat (wt%) and varying amounts of ETrA at two different dietary levels of linoleic acid (LA), approximately 4.4 and 19% of total fatty acids. These diets were fed to 5-week-old Dark Agouti rats for four weeks. Plasma lipid fractions and liver, spleen, and peritoneal exudate (PE) cells were analyzed for fatty acid composition. ETrA was present at up to 20% total fatty acids in plasma triglyceride, cholesterol ester, and phospholipid fractions. ETrA also accumulated to substantial levels in phospholipids of liver and spleen (up to 15% of total fatty acids) and PE cells (up to 11%). ETrA was found in plasma and tissue phospholipids in proportion to the amount of ETrA present in the diet. The incorporation was reduced in diets with higher LA content compared to diets containing similar amounts of ETrA but lower LA. All rats remained apparently healthy, and histological survey of major organs revealed no abnormality. While the long-term implications for health of ingestion of diets rich in ETrA remain to be established, rats appear to tolerate high levels of dietary ETrA without adverse effects. Dietary enrichment with ETrA warrants further investigation for possible beneficial effects in models of inflammation and autoimmunity, as well as in other conditions in which mediators derived from n-6 fatty acids can affect homeostasis adversely.     

Lung surfactant and fatty acid composition of lung tissue and lavage of rats fed diets containing different lipids

Two nutritional models, essential fatty acid (EFA) deficiency and the feeding of saturated vs unsaturated fats, were used to determine the effects of dietary lipids on the fatty acid composition of rat lung and lavage. Semipurified diets containing 7% corn oil, 7% hydrogenated coconut oil (EFA-deficient), 10% butter or 10% safflower oil were fed to dams during lactation and thereafter to their offspring for a total of 24 weeks. Lipids were extracted from the lung lavage and lung tissue and their fatty acid composition was determined. The content of dipalmitoylphosphatidylcholine (DPPC), the main surfactant in the lungs, was also determined. The results show that the levels of DPPC in the lungs of rats fed 10% butter decreased although the decrease in the EFA-deficient rats was greater. Comparing rats fed butter with those fed corn oil, there were also modifications in the fatty acid composition of the total lipids and phospholipids of lung tissue and lavage as well as in phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol +phosphatidylserine fractions isolated from the lung tissue. The changes in fatty acid composition were somewhat fewer in rats fed butter then in those fed an EFA-deficient diet. The results suggest that a marginal EFA deficiency produced in rats by long-term feeding of 10% butter may account for the reduction in DPPC levels and in the changes in fatty acid composition in the lung tissue and lavage.     

Low-fat diets do not lower plasma cholesterol levels in healthy men compared to high-fat diets with similar fatty acid composition at constant caloric intake

In most studies reporting the effects of high-fat (HF) and low-fat (LF) diets on human plasma fatty acids (FA) and lipoprotein levels, the design involved adding to the diet an oil that had an FA composition (FAC) very different from the FAC of the control diet. Thus, it is difficult to determine if simply reducing the fat content of the diet without changing the dietary FAC changes the tissue FAC or alters plasma lipid levels. In this study, we fed diets that contained either 22 or 39% of calories from fat, but had no differences in their FAC, for 50 d to a group (n=11) of healthy men (20–35 y). Thus, the polyunsaturated/saturated ratios (1.0) of the diets were identical as were the n−3/n−6 ratio and the monounsaturated-to-total fat ratios. The diets contained (wt% of total fat) approximately 28% saturated FA, 33% monounsaturatedcis-FA, 6% monounsaturatedtrans-FA, 22% n−6 polyunsaturated FA, and 7% n−3 polyunsaturated FA, and 4% other minor FA. The diets consisted of natural foods and were formulated to contain 16 en% protein, either 45 or 62 en% carbohydrate (CHO) and at least the recommended dailyallowance for all micronutrients. Both diets contained 360 mg of cholesterol per day. All subjects were given the HF diet for 20 d, and then six were placed on the LF and the other five remained on the HF diet for 50 d. The two groups were crossedover for the remaining 50 d of the study. The subjects' baseline total cholesterol level was 173 mg/dl, after 50 d on the HF diet it was 177 mg/dl and after 50 d on the LF diet, 173 mg/dl. The differences were not significant, and there were no significant changes in either the LDL or HDL cholesterol levels with either diet. Triglyceride levels, and consequently very low density lipoprotein levels, rose significantly on the LF, higher CHO diet compared to the levels found in the subjects on the HF diet (91.5 and 66.4 mg/dl respectively,P<0.002). The linoleic acid content of the plasma, platelets, and red blood cells was significantly (P<0.05) reduced in the LF diet compared to HF diet, without any obvious physiological effects. Hence, many earlier observations indicating reductions in plasma lipid levels when people are on LF diets may be due to changes in the FAC of the diet, not the reduction in fat calories.     

Effect of dietary columbinic acid on the fatty acid composition and physical membrane properties of different tissues of EFA-deficient rats

The effect of columbinic acid (5 trans, 9 cis, 12 cis, octadeca-trienoic acid) supplemented to a fat-free diet on the fatty acid composition and its correlation to the physical properties of several tissues of rats, was studied. The absence of lipids in the diet produced the typical changes in the fatty acid composition characteristic of essential fatty acid (EFA) deficiency, namely a significant increase in the relative percentage of monoenoic fatty acids with a concomitant decrease in linoleic and arachidonic acids and a rise in eicosa-5,8,11-trienoic acid in liver, kidney, lung and spleen homogenates. Columbinic acid supplemented to a fat-free diet for 24 or 48 hr was incorporated into the different tissues and was partially elongated to 7 trans, 11 cis, 14 cis eicosatrienoic acid, but it was not desaturated. It modified the fatty acid spectrum of the lipids in the different tissues returning it to a similar composition of non-EFA deficient animals, except for a decrease of linoleic acid. The absence of lipids in the diet produced an increase in the 1-6 diphenyl-1,3,5-hexatriene (DPH) steady-state fluorescence anisotropy (rs) in liver microsomes, that was corrected by the administration of columbinic acid for 24 hr. It is concluded that columbinic acid produced a change in the pattern of total fatty acid composition of the different tissues studied which induced a favorable effect on the physical properties of the liver microsomal membranes (rs), leading to an improvement on the fatty acid deficiency in those membranes. Besides, columbinic acid would also exert a favorable effect in the short term, but not in the long-term eicosanoids production.     

Effect of growth conditions on the fatty acid composition ofListeria monocytogenes and comparison with the fatty acids ofErysipelothrix andCorynebacterium

Six strains ofListeria monocytogenes belonging to four different serotypes all had similar fatty acid profiles when grown at 37 C, with C₁₅ and C₁₇ branched chain acids as major components. The proportion of 17∶0 br decreased markedly as the growth temperature was lowered from 37 C to 4 C, and a reduction of 18∶1 with increasing age of cultures was observed in cells harvested at different stages of the growth curve. The fatty acid composition was also affected by the nature of the culture medium. Two other genera of the family Corynebacteriaceae were analyzed for fatty acid composition. Strains ofErysipelothrix rhusiopathiae isolated from human, turkey, dog and pig had rather similar patterns, consisting mainly of straight chain, even-numbered fatty acids from C₁₀ to C₁₈. The three species ofCorynebacterum analyzed each had quite different fatty acid patterns.C. poinsettiae bore some resemblance toL. monocytogenes butC. pseudodiphtheriticum had much higher proportions of 16∶0 and 18∶1 andC. equi contained a rather complex mixture of fatty acids. Part of this work was carried out in the Collip Medical Research Laboratory.     

Effect of culture temperature on fatty acid composition ofChlorella sorokiniana

Chlorella sorokiniana was grown for extraction of fatty acids at seven temperatures ranging from 14 C to 38 C. The predominant fatty acids inC. sorokiniana grown at 38 C were saturated (46% of total); at 22 C, triunsaturated (40% of total); and at 14 C diunsaturated (47% of total). Increasing temperature resulted in an increase in the degree of unsaturation from 14 C to 22 C, but further increases in temperature always resulted in a decrease in unsaturation. At any point in the temperature range used, an increased temperature always resulted in fatty acids with a lower average chain length. Total fatty acid production was greatest at the extremes of temperature and lowest at 26 C. The chain length and degree of saturation of fatty acids increased at temperatures lower than 22 C. Therefore, the fatty acids ofC. sorokiniana do not have an increasingly lower melting point when the culture temperature is reduced at temperatures 22 C or below. Scientific Article No. A1562 Contribution No. 4271 of the Maryland Agricultural Experiment Station.     

Effect of altered fatty acid composition on soybean oil stability

During the last 15 years, hybridization and induced mutation breeding of soybeans have been successful in producing an altered fatty acid composition in the extracted oil. The objective of those investigations was to produce a low-linolenic acid soybena oil. Crude oils extracted from the seeds of three such genotypes were processed in laboratory simulations of commercial procedures to finished deodorized oils. Analysis of the fatty acid composition of the three oils showed the linolenic acid content to be 3.3%, 4.2% and 4.8%. The stability of these finished oils was compared to that of oil from a soybean variety having a linolenic acid content of 7.7% and of a commercial hydrogenated-winterized soybean oil (3.0% linolenic acid). Test and control oils were evaluated by a trained sensory panel initially, after accelerated storage at 60 C and during use at 190 C in room tests. Peroxide values were determined at the time of sensory evaluation. Results indicated there was no significant difference in flavor stability during storage between test and control oils. There was no significant difference, between the oils, in peroxide development during accelerated storage. Compared to control oils, the test oils had improved overall room odor intensity scores and lacked the fishy odors of non-hydrogenated soybean oil and the hydrogenated odors of commercial cooking oil. Presented at the AOCS meeting in Honolulu, HI in May 1986.     

Phospholipid fatty acid composition and stereospecific distribution of soybeans with a wide range of fatty acid composition

Phospholipid (PL) fatty acid composition and stereospecific distribution of 25 genetically modified soybean lines with a wide range of compositions were determined by gas chromatography and phospholipase A₂ hydrolysis. Pl contained an average of 55.3% phosphatidylcholine, 26.3% phosphatidylethanolamine, and 18.4% phosphatidylinositol. PL class proportions were affected by changes in overall fatty acid composition. PL fatty acid composition changed with oil fatty acid modification, especially for palmitate, stearate, and linolenate. Stereospecific analysis showed that saturated fatty acids were primarily located at the sn-1 position of all PL, and changes of the saturates in PL were largely reflected on this position. Oleate was distributed relatively equally between the sn-1 and sn-2 positions. Linoleate was much more concentrated on sn-2 than on sn-1 position for all PL. Linolenate was distributed relatively equally at low concentration but preferred sn-2 position at high concentration.     

Effect of dietary fat on phospholipid class distribution and fatty acid composition in rat fat cell plasma membrane

The effect of dietary fats on phospholipid class distribution and fatty acid composition was studied in rat fat cell plasma membrane. Three groups of male Wistar weanling rats were fed for 8 wk three diets differing in the amount and nature of the fats: 1.5% sunflower oil (low fat control; LFC), 10% sunflower oil (high fat, unsaturated; HFU), 1.5% sunflower oil+8.5% cocoa butter (high fat, saturated; HFS). Plasma membranes were prepared from epididymal adipocytes. The amount and type of dietary fat significantly altered membrane phospholipid distribution. Phospholipid content was lowered with HFU as compared to LFC or HFS diets, but no changes were observed for cholesterol. Phosphatidylinositol (PI) and phosphatidylserine (PS) were less affected by dietary changes than were other phospholipid classes. Major changes were detected for phosphatidylcholine (PC), phosphatidylethanolamine (PE) and sphingomyelin (SM) contents. No large changes in PC and PE fatty acid compositions were observed between the LFC and HFS groups, but the HFU diet induced several changes. Correlations with plasma membrane 5′-nucleotidase activities are discussed.     

The effect of conjugated linoleic acid on plasma lipoproteins and tissue fatty acid composition in humans

Conjugated linoleic acid (CLA) has been suggested by some animal studies to possess antiatherogenic properties. To determine, in humans, the effect of dietary CLA on blood lipids, lipoproteins, and tissue fatty acid composition, we conducted a 93-d study with 17 healthy female volunteers at the Metabolic Research Unit of the Western Human Nutrition Research Center. Throughout the study, subjects were fed a low-fat diet [30 energy percent (en%) fat, 19 en% protein, and 51 en% carbohydrate] that consisted of natural foods with the recommended dietary allowances for all known nutrients. After a 30-d stabilization period, subjects were randomly assigned to either an intervention group (n=10) supplemented daily with capsules containing 3.9 g of CLA or a control group (n=7) that received an equivalent amount of sunflower oil. The CIA capsules (CLA 65%) contained four major cis/trans geometric isomers (11.4% 9 cis-,11 trans-18∶2; 10.8% 8 trans-,10 cis-18∶2; 15.3% 11 cis-,13 trans-18∶2; and 14.7% 10 trans-, 12 cis-18∶2) and their corresponding cis/cis (6.74% total) and trans/trans (5.99% total) varieties in smaller amounts. Fasting blood was drawn on study days 30 (end of the stabilization period), 60 (midpoint of the intervention period), and 93 (end of the intervention period). Adipose tissue samples were taken on days 30 and 93. CLA supplementation for 63 d did not change the levels of plasma cholesterol, low density lipoprotein cholesterol, high density lipoprotein cholesterol, and triglycerides. The weight percentage of CLA in plasma increased from 0.28±0.06 to 1.09±0.31 (n=10, P<0.05) after the supplementation. The 9 cis-,11 trans-isomer was the most prominent variety followed by the 11 cis-,13 trans- and 10 trans-,12 cis-isomers in lesser amounts. CLA in adipose tissue was not influenced by the supplementation (0.79±0.18 to 0.83±0.19 wt%) (n=10) and the 9 cis-,11 trans-variety was the only isomer present. Thus, contrary to findings from some animal studies, CLA does not seem to offer health benefits, in the short term, regarding the prevention of atherosclerosis in humans. CLA supplementation for 2 mon did not alter the blood cholesterol or lipoprotein levels of healthy, normolipidemic subjects. The supplementation did increase CLA in the plasma but only 4.23% of the ingested CLA was present in the plasma at any given time. No adverse effect of CLA supplementation was detected in this study.     

Diet-induced changes in the fatty acid composition of mouse hepatocyte plasma membranes

Hepatocyte plasma membranes were isolated from the livers of mice fed either a low fat diet or high fat diets containing polyunsaturated or saturated fat. The combined rate and isopycnic ultracentrifugation technique which was used produced highly purified hepatocyte plasma membrane fractions. The efficacy of the procedure was checked by electron microscopy and the assay of marker enzymes for the different subcellular organelles. Mice were maintained on a low fat diet until 60–70 days of age, when they were fed high fat diets containing polyunsaturated or saturated fat. The hepatocyte plasma membrane lipids of mice fed the polyunsaturated fat diet for 4 wk contained increased proportions of the major dietary unsaturated fatty acid, linoleic acid, and increased proportions of arachidonic acid. The proportion of linoleic and arachidonic acids decreased with continued feeding of the polyunsaturated fat diet. The hepatocyte plasma membrane lipids of mice fed the saturated fat diet contained increased proportions of oleic acid.     

The effect of dietary docosahexaenoic acid on plasma lipoproteins and tissue fatty acid composition in humans

Normal, healthy male volunteers (n=6) were fed diets [high docosahexaenoic acid-DHA] containing 6 g/d of DHA for 90 d. The stabilization (low-DHA) diet contained less than 50 mg/d of DHA. A control group (n=4) remained on the low-DHA diet for the duration of the study (120 d). Blood samples were drawn on study days 30 (end of the stabilization period), 75 (midpoint of the intervention period), and 120 (end of the intervention period). Adipose tissue (AT) samples were taken on days 30 and 120. The plasma cholesterol (C), low density lipoprotein (LDL)-C and apolipoproteins (apo) [Al, B, and lipoprotein (a)] were unchanged after 90 d, but the triglycerides (TAG) were reduced from a mean value of 76.67±24.32 to 63.83±16.99 mg/dL (n=6, P<0.007 using a paired t-test) and the high density lipoprotein (HDL)-C increased from 34.83±4.38 mg/dL to 37.83±3.32 mg/dL (n=6, P<0.017 using a paired t-test). The control group showed no significant reduction in plasma TAG levels. Apo-E, however, showed a marked increase in the volunteers’ plasma after 90 d on the high-DHA diet, from 7.06±4.47 mg/dL on study day 30 to 12.01±4.96 mg/dL on study day 120 (P<0.002 using a paired t-test). The control subjects showed no significant change in the apo-E in their plasma (8.46±2.90 on day 30 vs. 8.59±2.97 on day 120). The weight percentage of plasma DHA rose from 1.83±0.22 to 8.12±0.76 after 90 d on the high-DHA diet. Although these volunteers were eating a diet free of eicosapentaenoic acid (EPA), plasma EPA levels rose from 0.38±0.05 to 3.39±0.52 (wt%) after consuming the high-DHA diet. The fatty acid composition of plasma lipid fractions—cholesterol esters, TAG, and phospholipid—showed marked similarity in the enrichment of DHA, about 10%, after the subjects consumed the high-DHA diet. The DHA content of these plasma lipid fractions varied from less than 1% (TAG) to 3.5% (phospholipids) at baseline, study day 30. EPA also increased in all plasma lipid fractions after the subjects consumed the high-DHA diet. There were no changes in the plasma DHA or EPA levels in the control group. Consumption of DHA also caused an increase in AT levels of DHA, from 0.10±0.02 to 0.31±0.07 (wt%) (n=6, P<0.001 using a paired t-test), but the amount of EPA in their AT did not change. Thus, dietary DHA will lower plasma TAG without EPA, and DHA is retroconverted to EPA in significant amounts. Dietary DHA appears to enhance apo-E synthesis in the liver. It appears that DHA can be a safe and perhaps beneficial supplement to human diets.     

Thermal adaptation affects the fatty acid composition of plasma phospholipids in trout

The online version of the original article can be found at     

Thermal adaptation affects the fatty acid composition of plasma phospholipids in trout

The adaptive changes in the fatty acid (FA) composition of plasma phospholipids (PL) in response to alterations in environmental water temperature were investigated in juvenile rainbow trout (Oncorhynchus mykiss). The changes observed during thermal adaptation from 22°C in summer to 8°C in winter were reproduced by laboratory cold acclimation (CA) at 6°C of 22°C-summer-acclimated animals. In cold-acclimated and winter-acclimated trout, the increase in the unsaturation of PL fatty acids was mainly due to an enrichment of approximately 7% in the total weight percentage of 22∶6n−3, while a concomitant significant decrease in the levels of 18∶0 and of the monoenoic n−9 FA was observed. A time course study revealed that the changes in PL fatty acids became significant after 10 d of CA and were complete after one month. These changes in the composition of the fatty acyl chains of plasma total PL indicate that the FA composition of plasma lipoprotein PL does not remain constant during thermal adaptation. This would suggest that plasma lipoproteins provide a rapid systemic supply of lipids containing more or less unsaturated FA during thermal adaptation of poikilothermic animals.     

Quantification,characterization and fatty acid composition of lysophosphatidic acid in different rat tissues

The amount and composition of lysophosphatidate present in different rat tissues have been estimated by an internal standard method in which a synthetic unnatural isomer (1-heptadecanoyl-rac-glycerol-3-phosphate) was added to the total lipid extracts, and the fatty acid composition of purified lysophosphatidate was determined. Lipids from tissues were extracted under acidic conditions, and the lysophosphatidate was purified by solvent partitions followed by thin-layer chromatography in multiple solvent systems. The purified lipid was shown to be 1-acyl-sn-glycerol-3-phosphate by chromatographic and chemical analysis, by its resistance to hydrolysis when treated with phospholipase A₂ and also by its complete conversion to 1-acyl-sn-glycerol when treated with alkaline phosphatase. The fatty acid consituents of this lipid were determined by gas-liquid chromatography of the derived methyl esters. The concentrations (nmol/g of tissue) of lysophosphatidate in various tissues were: 86.2±4.2 in brain, 60.3±6.3 in liver, 46.4±6.5 in kidney, 30.6±5.0 in testis, 22.3 in heart and 19.3 in lung. Mostly (80%) saturated fatty acids were found to be present in this lyso lipid. A significantly high level of stearic acid was present in this lipid from all the tissues (50–60% in liver, kidney, brain and testis, and about 40% in heart and lung) compared to plamitic acid (10–15% in liver, kidney and brain and 25–30% in testis, heart and lung). The fatty acid compositions of phosphatidic acid, the putative product of lysophosphatidate acylation, from different tissues were also determined and palmitate was found to be the major saturated fatty acid. These results suggest that tissue lysophosphatidic acid is not only formed byde novo biosynthesis but is also generated via the breakdown of phospholipids such as phosphoinositides.     

Effect of essential fatty acid deficiency on lipid composition of basolateral plasma membrane of pig intestinal mucosal cells

The effect of essential fatty acid (EFA) deficiency on the lipid composition of basolateral plasma membranes (BPM) from intestinal mucosal cells was investigated in weaning pigs fed control or EFA-deficient diets for 12 weeks. The phospholipid and cholesterol contents relative to protein were similar in both groups, showing a cholesterol/phospholipid molar ratio of 0.6. The distribution of phospholipid classes was also unaffected by the diet. In contrast, fatty acid profiles of the two phospholipid main classes, phosphatidylcholine and phosphatidylethanolamine were altered by EFA deficiency. Linoleic acid (18∶2n−6) was largely reduced, whereas arachidonic acid (20∶4n−6) only slightly decreased in EFA-deficient pigs. The unsaturation index was essentially maintained by high levels of oleic acid (18∶1n−9) and by conversion of oleic acid to 5,8,11-eicosatrienoic acid (20∶3n−9). Finally, during the period of EFA deficiency, the lipid composition of BPM of the intestinal mucosal cells was little affected, suggesting a preferential uptake of 20∶4n−6 and (or) precursor mobilized from other tissues. However, an effect of dietary treatment on the function of membrane-associated proteins cannot be ruled out.     

Effect of diets rich in linoleic or α-linolenic acid on phospholipid fatty acid composition and eicosanoid production in atlantic salmon (Salmo salar)

Atlantic salmon post-smolts were fed diets rich in linoleic acid (sunflower oil, SO), α-linolenic acid (linseed oil, LO) or long-chain polyunsaturated fatty acids (fish oil, FO) for a period of 12 wk. In the liver phospholipids of fish fed SO, the levels of 18∶2n−6, 20∶2n−6, 20∶3n−6 and 20∶4n−6 were significantly elevated compared to both other treatment. In choline phospholipids (CPL), ethanolamine phospholipids (EPL) and phosphatidylserine (PS) the levels of 22∶4n−6 and 22∶5n−6 were significantly elevated in fish fed SO. In liver phospholipids from fish fed LO, 18∶2n−6, 20∶2n−6 and 20∶3n−6 were significantly elevated but 20∶4n−6, 22∶4n−6 and 22∶5n−6 were similar or significantly decreased compared to fish fed FO. Liver phospholipids from fish fed LO had increased 18∶3n−3 and 20∶4n−3 compared to both other treatments while EPL and phosphatidylinositol (PI) also had increased 20∶5n−3. In fish fed LO, 22∶6n−3 was significantly reduced in CPL, PS and PI compared to fish fed FO. Broadly similar changes occurred in gill phospholipids. Production of 12-lipoxygenase metabolites in isolated gill cells stimulated with the Ca²⁺-ionophore A23187 were significantly reduced in fish fed either SO or LO compared to those fed FO. However, the ratio 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE)/12-hydroxy-5,8,10,14,17-eicosapentaenoic acid (12-HEPE) was significantly elevated in stimulated gill cells from SO-fed fish. Although mean values of thromboxane B₂ (TXB₂) and prostaglandin E₂ (PGE₂) were increased in fish fed SO, they were not significantly different from those of the other two treatments.